python中使用sys模板和logging模块获取行号和函数名的方法

对于python，这几天一直有两个问题在困扰我:
1.python中没办法直接取得当前的行号和函数名。这是有人在论坛里提出的问题，底下一群人只是在猜测python为什么不像__file__一样提供__line__和__func__，但是却最终也没有找到解决方案。
2.如果一个函数在不知道自己名字的情况下，怎么才能递归调用自己。这是我一个同事问我的，其实也是获取函数名，但是当时也是回答不出来。

但是今晚！所有的问题都有了答案。
一切还要从我用python的logging模块说起，logging中的format中是有如下选项的:

％(name)s            Name of the logger (logging channel)
％(levelno)s         Numeric logging level for the message (DEBUG, INFO,
                    WARNING, ERROR, CRITICAL)
％(levelname)s       Text logging level for the message ("DEBUG", "INFO",
                    "WARNING", "ERROR", "CRITICAL")
％(pathname)s        Full pathname of the source file where the logging
                    call was issued (if available)
％(filename)s        Filename portion of pathname
％(module)s          Module (name portion of filename)
％(lineno)d          Source line number where the logging call was issued
                    (if available)
％(funcName)s        Function name
％(created)f         Time when the LogRecord was created (time.time()
                    return value)
％(asctime)s         Textual time when the LogRecord was created
％(msecs)d           Millisecond portion of the creation time
％(relativeCreated)d Time in milliseconds when the LogRecord was created,
                    relative to the time the logging module was loaded
                    (typically at application startup time)
％(thread)d          Thread ID (if available)
％(threadName)s      Thread name (if available)
％(process)d         Process ID (if available)
％(message)s         The result of record.getMessage(), computed just as
                    the record is emitted

也就是说，logging是能够获取到调用者的行号和函数名的，那会不会也可以获取到自己的行号和函数名呢？
我们来看一下源码，主要部分如下:

def currentframe():
    """Return the frame object for the caller's stack frame."""
    try:
        raise Exception
    except:
        return sys.exc_info()[2].tb_frame.f_back
def findCaller(self):
    """
    Find the stack frame of the caller so that we can note the source
    file name, line number and function name.
    """
    f = currentframe()
    #On some versions of IronPython, currentframe() returns None if
    #IronPython isn't run with -X:Frames.
    if f is not None:
        f = f.f_back
    rv = "(unknown file)", 0, "(unknown function)"
    while hasattr(f, "f_code"):
        co = f.f_code
        filename = os.path.normcase(co.co_filename)
        if filename == _srcfile:
            f = f.f_back
            continue
        rv = (co.co_filename, f.f_lineno, co.co_name)
        break
    return rv
def _log(self, level, msg, args, exc_info=None, extra=None):
    """
    Low-level logging routine which creates a LogRecord and then calls
    all the handlers of this logger to handle the record.
    """
    if _srcfile:
        #IronPython doesn't track Python frames, so findCaller throws an
        #exception on some versions of IronPython. We trap it here so that
        #IronPython can use logging.
        try:
            fn, lno, func = self.findCaller()
        except ValueError:
            fn, lno, func = "(unknown file)", 0, "(unknown function)"
    else:
        fn, lno, func = "(unknown file)", 0, "(unknown function)"
    if exc_info:
        if not isinstance(exc_info, tuple):
            exc_info = sys.exc_info()
    record = self.makeRecord(self.name, level, fn, lno, msg, args, exc_info, func, extra)
    self.handle(record)

我简单解释一下，实际上是通过在currentframe函数中抛出一个异常，然后通过向上查找的方式，找到调用的信息。其中

rv = (co.co_filename, f.f_lineno, co.co_name)

的三个值分别为文件名，行号，函数名。(可以去http://docs.python.org/library/sys.html来看一下代码中几个系统函数的说明)
OK，如果已经看懂了源码，那获取当前位置的行号和函数名相信也非常清楚了，代码如下:

#!/usr/bin/python
# -*- coding: utf-8 -*-
'''
#=============================================================================
#  FileName:        xf.py
#  Description:     获取当前位置的行号和函数名
#  Version:         1.0
#=============================================================================
'''
import sys
def get_cur_info():
    """Return the frame object for the caller's stack frame."""
    try:
        raise Exception
    except:
        f = sys.exc_info()[2].tb_frame.f_back
    return (f.f_code.co_name, f.f_lineno)

def callfunc():
    print get_cur_info()

 
if __name__ == '__main__':
    callfunc()

输入结果是:

('callfunc', 24)

符合预期~~
哈哈，OK！现在应该不用再抱怨取不到行号和函数名了吧~

=============================================================================
后来发现，其实也可以有更简单的方法，如下:

import sys
def get_cur_info():
    print sys._getframe().f_code.co_name
    print sys._getframe().f_back.f_code.co_name
get_cur_info()

调用结果是:

get_cur_info
<module>